Compounds- two or more different elements combined chemically



Metals- located to the left of the staircase on the periodic table. Shiny, conduct electricity, heat conductors, malleability and ductility. Always makes positive ions, cations.

Nonmetals- elements to the right of the staircase. Usually found as compounds or mixtures of compounds. Always makes negative ions, anions.

Metalloids- elements touching the staircase. Share properties of both metals and nonmetals.

Compounds- two or more different elements combined chemically.

Molecule- an electrically neutral group of atoms that act as a unit, due to sharing of electrons. Molecules of a given compound are all identical.

Molecular compounds- compounds that are composed of molecules where electron sharing has taken place. Tend to have low melting points, gases or liquids at room temperature, and are composed of two or more nonmetallic elements. (CO, H2O, C12H22O11)

Ionic compounds- composed of positive cations and negative anions, where electrons are transferred from one atom to another. When formed, ionic compounds are electrically neutral. Usually formed from metallic and nonmetallic elements, most are crystalline solids at room temperature.

Chemical formula- shows the kinds and numbers of atoms in the smallest representative unit of the substance.

Molecular formula shows the number and kinds of atoms present in a molecule of a compound.

Diatomic molecules- HOFBrINCl Only molecules that exist in nature in pairs.

Formula unit- the lowest whole number ratio of ions in an ionic compound.

Law of definite proportions- in samples of any chemical compound the masses of the elements are always in the same proportions.

Law of multiple proportions- whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.

Oxidation numbers- the ionic charges of representative elements. Found by looking at the periodic table. –ous is for the lower of the two ionic charges, -ic is for the higher.

Polyatomic ions- are tightly bound groups of atoms that behave as a unit and carry their own charge. –ite polyatomic ions have one less oxygen atom than –ate polyatomic ions. (see the list on p.123)

Binary compounds- are composed of two elements. Ionic binary compounds are composed of one cation and one anion. Cation goes first in the writing process. Charges must equal zero.

Naming binary compounds- you start by naming the cation, followed by naming the anion with an –ide ending. Roman numerals are used following the cation to identify which oxidation state the cation is in.

Ternary compounds- contains atoms of three different elements. These usually deal with polyatomic ions. Start with naming the cation followed by naming the polyatomic ion.

Binary molecular compounds- composed of two nonmetallic elements. To name binary molecular compounds you must use prefixes. If there is a single atom of the first element, the mono- is usually dropped from the name.

Big Six Acid Names- HCl, H2SO4, HNO3, HC2H3O2, H3PO4, H2CO3

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